Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of the common general knowledge in the field.
Processes for the treatment of wastewater are known which include biological steps, in which the wastewater is treated with micro-organisms; and separation steps, in which liquids and solid material are separated.
The biological steps require that the wastewater be aerated and mixed or agitated. Some known methods and systems for the treatment of wastewater use fine bubble diffusers to aerate the wastewater and a separate mixing device to effect mixing and agitation.
It is recognised that the processing of wastewater having higher mixed liquor suspended solids (MLSS) has certain advantages. Unfortunately the use of fine bubble diffusers in the processing of high MLSS wastewater is inconvenient for two main reasons. One reason is that as the mixed liquor concentration increases, the efficiency of the diffuser greatly decreases. A second reason is that fine bubble diffusers foul more rapidly in a very high suspended solids environment and require more maintenance and more frequent replacement.
Further known systems use gas jets to aerate the wastewater. When compared with fine bubble diffusers, the use of jets is advantageous in a number of respects. For example, alpha values for Jet aeration systems tend to be higher generally than those for diffusers, in part due to higher mixing forces generated by jet aeration. Further, jet aerators tend to retain their higher alpha values during operation, even at higher MLSS. Jet aeration also serves to agitate and mix the wastewater, eliminating or reducing the need for separate mixing and agitation.
However, the running costs of the blowers used with jet aerators are highly energy intensive and may add significantly to the operating costs. It is an object of the present invention to overcome or alleviate at least one of the disadvantages of the prior art, or to provide a useful alternative.